Domains of Life: Archaea, Bacteria, and Eukarya

• The three domains of life are Archaea, Bacteria, and Eukarya.
• Archaea and Bacteria are prokaryotic domains.
• The ribosomal RNA gene is sequenced and compared to generate the phylogenetic tree of life.
• Ribosomes consist of protein subunits and ribosomal ribonucleic acid (RNA).
• DNA genome, ribosomes, membrane, and cytoplasm are structures common to all living cells.
• Prions and viruses are two types of non-living infectious agents.
• Prions are acellular and composed of protein only; they affect mammals and cause neurological diseases.
• Viruses are acellular, consist of nucleic acid (DNA or RNA) and protein, and lack a cell membrane. Viruses depend on a host cell for reproduction.
• Algae, protists, protozoa, and fungi are eukaryotic.

Prokaryotes vs. Eukaryotes

• Prokaryotes lack a nucleus and organelles, have a smaller cell size, and smaller/lighter 70S ribosomes.
• Eukaryotes possess a nucleus and organelles, have a larger cell size, and larger/heavier 80S ribosomes.

Benefits of Microbes

• Aid in the development of human intestines.
• Good bacteria occupies space, preventing pathogens from taking up space, limits resources therefore pathogens cannot compete
• Help maintain oxygen levels and nutrient cycling/decomposition.
• Break down cellulose in plants and assist in bioremediation/waste treatment.
• Reduce inflammation in the gut by producing short chain fatty acids.

Location of Microbes in the Human Body

• Skin and its contiguous mucous membranes.
• Upper respiratory tract (oral cavity, pharynx, nasal cavity).
• GI tract (mouth, colon, rectum, anus).
• Outer opening of the urethra.
• External genitalia.
• Vagina.
• External ear canal.
• External eye (lids and follicles).
• Most microbes are beneficial.
• Microbes exist everywhere in the environment.

Taxonomic Groupings in Bacteriology

• The primary taxonomic groupings used are Genus, species, and strain (subspecies).
• Genus is always capitalized.
• species is always in lowercase.
• Genus species can be italicized or underlined.
• The abbreviation for Genus, G. species, is also used.

Learn about the three domains of life: Archaea, Bacteria, and Eukarya. Discover the characteristics of prokaryotes and eukaryotes, including cell structure and ribosomes. Explore non-living infectious agents like prions and viruses, and eukaryotic microorganisms like algae and fungi.